1. Field of the Invention
The present invention relates to wireless IC devices and in particular relates to a wireless IC device, a wireless IC module and a method of manufacturing a wireless IC module preferably for use in radio frequency identification (RFID) systems that perform communication of data in a non-contact manner.
2. Description of the Related Art
In recent years, wireless IC devices have been developed to include a wireless IC chip that electronically stores information for managing articles and processes predetermined radio signals, and an antenna that transmits and receives radio signals between the wireless IC chip and a reader/writer. Systems that use such wireless IC devices are referred to as RFID systems and can be used in authentication of individuals and transmission and reception of data by using in combination with each other a wireless IC device (taking the form of a card, tag, inlet or the like) and a reader/writer that reads and writes data from and to the wireless IC device.
In such a non-contact RFID system, when an article, which is a target to which a wireless IC device has been attached, contains metal, moisture, salt or the like, sometimes an eddy current is generated in the article and the antenna does not behave correctly due to the effect of the eddy current. That is, when an antenna is affixed to a surface of an article, there are cases where the transmission or reception of information contains errors or is not possible due to the electromagnetic waves being absorbed by the eddy current. This defect has been particularly prominent in wireless IC devices that operate in a high frequency band.
Accordingly, for example, there is a technique in which a magnetic member is disposed between the antenna and the article in wireless IC devices operating in a HF band as disclosed in Japanese Unexamined Patent Application Publication No. 2004-304370, Japanese Unexamined Patent Application Publication No. 2005-340759 and Japanese Unexamined Patent Application Publication No. 2006-13976. Furthermore, there is a technique in which the antenna is disposed so as to be spaced apart from the article in wireless IC devices operating in a UHF band, as disclosed in Japanese Unexamined Patent Application Publication No. 2007-172369 and Japanese Unexamined Patent Application Publication No. 2007-172527.
However, in the technique in which a magnetic member is disposed between the antenna and the article and in the technique in which the antenna is spaced apart from the article, there has been a problem in that the wireless IC device cannot be reduced in size and thickness, which are desired in order to apply the device in diverse applications.